Abstract

The localization of block in atrioventricular conduction was determined in 15 subjects with first- second-and third-degree block by recording His-bundle (H) electrograms via a tripolar electrode catheter positioned across the tricuspid valve. The H potential was recorded as a biphasic or triphasic spike occurring within the P-R interval of the standard electrocardiogram (EKG) and between the atrial and ventricular electrograms. Measurements in milliseconds were made of the intervals from the P wave to the His (P-H interval) and from the His to the Q wave of the QRS (H-Q interval). In all subjects with first-degree heart block (congenital, acquired, and